California Code, Code of Civil Procedure - CCP § 645.1

(a) When a referee is appointed pursuant to Section 638, the referee's fees shall be paid as agreed by the parties. If the parties do not agree on the payment of fees and request the matter to be resolved by the court, the court may order the parties to pay the referee's fees as set forth in subdivision (b).

(b) When a referee is appointed pursuant to Section 639, at any time after a determination of ability to pay is made as specified in paragraph (6) of subdivision (d) of Section 639, the court may order the parties to pay the fees of referees who are not employees or officers of the court at the time of appointment, as fixed pursuant to Section 1023, in any manner determined by the court to be fair and reasonable, including an apportionment of the fees among the parties. For purposes of this section, the term “parties” does not include parties' counsel.